Methods and devices for jetting viscous medium on workpieces

ABSTRACT

An apparatus for depositing and/or jetting viscous medium on a surface of a workpiece includes at least two depositing head assemblies. The at least two depositing head assemblies are configured to move in three dimensional space. The at least two depositing head assemblies are also configured to at least one of concurrently and simultaneously deposit the viscous medium on the workpiece.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of, and claims priority under 35 U.S.C.§ 120 to, U.S. application Ser. No. 14/218,243, filed Mar. 18, 2014,which claims priority under 35 U.S.C. § 119(e) to ProvisionalApplication No. 61/799,799, filed on Mar. 15, 2013, and which is acontinuation of International Application No. PCT/EP2014/054987, filedon Mar. 13, 2014, which also claims priority to Provisional ApplicationNo. 61/799,799, filed on Mar. 15, 2013, the entire contents of all ofwhich are incorporated herein by reference.

BACKGROUND

Conventionally, deposits are formed on workpieces (e.g., substrates)prior to mounting components by jetting droplets of viscous medium(e.g., solder paste, glue, etc.) onto the workpiece. A conventionaljetting system generally includes: a nozzle space for containing arelatively small volume of viscous medium prior to jetting; a jettingnozzle coupled to the nozzle space; an impacting device for impactingand jetting the viscous medium from the nozzle space through the jettingnozzle in the form of droplets; and a feeder to feed the medium into thenozzle space.

FIG. 1 illustrates an example of a conventional machine 1 to jetdroplets of a viscous medium onto a workpiece 2.

Referring to FIG. 1, the machine 1 includes an X-beam 3 and an X-wagon 4connected to the X-beam 3 via an X-rail 16 and reciprocally movablealong the X-rail 16. The X-beam 3 is reciprocally and movably connectedto a Y-rail 17, thereby being movable in directions perpendicular to theX-rail 16. The Y-rail 17 is rigidly mounted in the machine 1. Movementof the X-wagon 4 and the X-beam 3 may be driven by linear motors (notshown).

A conveyer 18 feeds the workpiece 2 through the jetting machine 1. Whenthe workpiece 2 is in the appropriate position under the X-wagon 4, alocking device 19 fixes the workpiece 2 in place. A camera 7 locatesfiducial markers on the surface of the workpiece 2 to determine theprecise position of the workpiece 2. Viscous medium is applied to theworkpiece 2 at desired locations by moving the X-wagon 4 over theworkpiece 2 in a given, desired or predetermined pattern and operating ajetting assembly 5 at given, desired or predetermined locations.

The machine 1 also includes an exchange assembly support 20 supportingfurther assemblies 22, and a vacuum ejector 6.

Since production speed is a relatively important factor in themanufacturing of electronic circuit boards, the application of viscousmedium is typically performed “on the fly”. Unfortunately, withconventional technology such as the jetting system shown in FIG. 1,production speed is somewhat limited.

SUMMARY

The technology disclosed provides methods and apparatuses for jettingviscous medium on a surface of a workpiece. The apparatuses include atleast two depositing head assemblies for depositing viscous medium, andat least one of the at least two depositing head assemblies is a jettinghead assembly.

According to at least one example implementation of the technologydisclosed, the at least two depositing head assemblies for depositingviscous medium include at least one jetting head assembly, where the atleast two depositing head assemblies are configured to move in threedimensional space, and are configured to at least one of concurrentlyand simultaneously deposit or jet the viscous medium on a workpiece.

According to at least one example implementation of the technologydisclosed, the apparatus includes: at least two jetting head assembliesconfigured to move in three dimensional space, and configured to atleast one of concurrently and simultaneously jet the viscous medium on aworkpiece.

According to at least some example implementations of the technologydisclosed, at least two jetting head assemblies may be configured tomove in three dimensions at least one of concurrently andsimultaneously, and may be further configured to shoot different dropletsizes or volumes. For example, a first jetting head assembly of the atleast two jetting head assemblies may be configured to deposit viscousmedium (e.g., solder paste) by shooting droplet volumes of about 5 nL,and a second jetting head assembly of the at least two jetting headassemblies may be configured to deposit viscous medium by shootingdroplet volumes of about 15 nL.

According to at least some example implementations of the technologydisclosed, at least two jetting head assemblies may be configured tomove in three dimensions at least one of concurrently andsimultaneously, and may further be configured to shoot viscous mediumwithin certain mutually different specified ranges of volumes. Forexample, a first jetting head assembly of the at least two jetting headassemblies may be configured to deposit viscous medium on a surface(e.g., solder paste) by shooting droplet volumes within the range ofabout 5-15 nL, and a second jetting head assembly of the at least twojetting head assemblies may be configured to deposit viscous medium on asurface by shooting droplet volumes within the range of about 10-20 nL.In another example implementation of the technology disclosed a firstjetting head assembly of the at least two jetting head assemblies may beconfigured to deposit viscous medium (e.g., solder paste) by shootingdroplet volumes within the range of about 10-20 nL, and a second jettinghead assembly of the at least two jetting head assemblies may beconfigured to deposit viscous medium by shooting droplet volumes withinthe range of about 1-5 nL. In another example implementation of thetechnology disclosed, a first jetting head assembly of the at least twojetting head assemblies may be configured to deposit viscous medium(e.g., solder paste) by shooting droplet volumes of about 4 nL, and asecond jetting head assembly of the at least two jetting head assembliesmay be configured to deposit viscous medium by shooting droplet volumesof about 10 nL.

According to at least some example implementations, the apparatus forjetting viscous medium may further include: a platform configured tohold the workpiece; a first beam arranged above the platform, a first ofat least two depositing head assemblies is a jetting head assembly beingmovably fixed to the first beam; and a second beam arranged above theplatform and in parallel with the first beam, a second of the at leasttwo depositing head assemblies being movably fixed to the second beam.The first jetting head assembly may be configured to move along thefirst beam in a first direction, and the second depositing head assemblymay be configured to move along the second beam in the first direction.The first and second beams may be configured to move in a seconddirection, which is perpendicular to the first direction. The first andsecond beams and the at least two depositing head assemblies may beconfigured to move at least one of simultaneously and concurrently. Thefirst and second depositing head assemblies (e.g., jetting headassemblies) may be further configured to move in a third direction,which is perpendicular to the first and second directions.

According to at least some example implementations, the apparatus forjetting viscous medium may further include: a platform configured tohold the workpiece; and a beam arranged above the platform, the at leasttwo depositing head assemblies including at least one jetting headassembly movably fixed to the beam. The at least two depositing headassemblies may be configured to move along the beam in a firstdirection. The beam may be configured to move in a second direction. Thebeam and the at least two jetting head assemblies may be configured tomove at least one of simultaneously and concurrently.

According to at least some example implementations, the at least twodepositing head assemblies include at least two jetting head assembliesthat are configured to at least one of: shoot different types/classes ofsolder pastes; shoot droplets with different shot sizes/ranges; andshoot droplets of various types of viscous media.

At least one other example implementation provides an apparatus forjetting viscous medium on a workpiece that is moving while jetting theviscous medium on the workpiece. According to at least this exampleembodiment, the apparatus includes: at least two supporting arrangements(e.g. cylindrical rollers) configured to move the workpiece in a firstdirection by transferring the workpiece from a first of the supportingarrangements to a second of the supporting arrangements; and at leastone jetting head assembly configured to move in at least the firstdirection and a second direction, the jetting head assembly beingfurther configured to jet the viscous medium on the workpiece at leastone of concurrently and simultaneously while the workpiece moves betweenthe first and second supporting arrangements (e.g., cylindricalrollers).

According to at least some example embodiments of this implementation,the workpiece may be a flexible substrate. The jetting head assembly mayinclude at least two jetting head assemblies configured to at least oneof: shoot different types/classes of solder pastes; shoot droplets withdifferent shot sizes/ranges; and shoot droplets of various types ofviscous media.

At least one other example implementation provides a linescan jettingapparatus for jetting viscous medium on a workpiece. According to atleast this example embodiment, the apparatus includes: a conveyorconfigured to carry the workpiece in a first direction; a first set ofbeams extending longitudinally between opposite sides of a jetting headassembly frame; a second set of beams extending longitudinally betweenthe first set of beams, the second set of beams including a first beamand a second beam; and a first jetting head assembly movably fixed tothe first beam, the first jetting head assembly being configured to movealong the first beam in a second direction, which is perpendicular tothe first direction; and a second jetting head assembly fixed to thesecond beam, the second jetting head assembly being configured to movealong the second beam in the second direction.

Another implementation of the technology disclosed provides for alinescan jetting apparatus for jetting viscous medium on a workpiece. Inthis example, the apparatus includes: a conveyor configured to carry theworkpiece in a first direction; a beam extending longitudinally betweenopposite sides of a jetting head assembly frame; and a single jettinghead assembly movably fixed to the beam, the first jetting head assemblybeing configured to move along the beam in a second direction, which isperpendicular to the first direction.

According to at least some example implementations of the technologydisclosed, the conveyor may be configured to move the workpieceincrementally through the linescan jetting apparatus. The first andsecond jetting head assemblies may be configured to at least one ofconcurrently and simultaneously jet viscous medium on the workpiece. Thefirst and second jetting head assemblies may be configured to move in athird direction, which is perpendicular to the first and seconddirections. The first and second jetting head assemblies may beconfigured to at least one of: shoot different types/classes of solderpastes; shoot droplets with different shot sizes/ranges; and shootdroplets of various types of viscous media.

At least one other example embodiment provides a linescan jettingapparatus for jetting viscous medium on a workpiece. According to atleast this example embodiment, the apparatus includes: a conveyorconfigured to carry the workpiece in a first direction; a first set ofbeams extending longitudinally between opposite sides of a jetting headassembly frame; at least one second beam extending longitudinallybetween the first set of beams; and a first jetting head assemblymovably fixed to the second beam, the first jetting head assembly beingconfigured to move along the first beam in a second direction, which isperpendicular to the first direction.

At least one other example embodiment provides a method for jettingviscous medium on a workpiece. According to at least this exampleembodiment, the method includes: moving at least two jetting headassemblies in three dimensional space; and jetting, at least one ofconcurrently and simultaneously by the at least two jetting headassemblies, the viscous medium on the workpiece.

According to at least some example embodiments, the method may furtherinclude: moving the at least two jetting head assemblies in threedimensions at least one of concurrently and simultaneously.

According to at least some example embodiments, the moving may include:moving a first of the at least two jetting head assemblies along a firstbeam arranged above a platform holding the workpiece; and moving asecond of the at least two jetting head assemblies along a second beamarranged above the platform and in parallel with the first beam. Thefirst jetting head assembly may move along the first beam in a firstdirection, and the second jetting head assembly moves along the secondbeam in the first direction.

According to at least some example embodiments, the moving at least twojetting head assemblies may further include: moving the first and secondbeams in a second direction, which is perpendicular to the firstdirection. The first and second beams and the at least two jetting headassemblies may move at least one of simultaneously and concurrently.

According to at least some example embodiments, the moving at least twojetting head assemblies may further include: moving the first and secondjetting head assemblies in a third direction, which is perpendicular tothe first and second directions. The at least two jetting headassemblies may move in a first direction along a beam arranged above aplatform holding the workpiece. The beam may move in a second direction.The beam and the at least two jetting head assemblies may move at leastone of simultaneously and concurrently.

According to at least some example embodiments, the jetting may includeat least one of: shooting different types/classes of solder pastes withthe at least two jetting assemblies; shooting droplets with differentshot sizes/ranges with the at least two jetting assemblies; and shootingdroplets of various types of viscous media with the at least two jettingassemblies.

At least one other example embodiment provides a method for jettingviscous medium on a workpiece. According to at least this exampleembodiment, the method includes: moving the workpiece in a firstdirection by transferring the workpiece from a first support arrangement(e.g., a cylindrical roller) to a second support arrangement; moving atleast one jetting head assembly in at least the first direction and asecond direction; and jetting, by the jetting head assembly, the viscousmedium on the workpiece at least one of concurrently and simultaneouslywhile the workpiece moves between the first and second supportarrangements (e.g., cylindrical rollers).

According to at least some example embodiments, the workpiece may be aflexible substrate. In other example implementations, the jetting may beperformed by at least two jetting head assemblies that are mutuallydifferent in their configurations in that they are configured to atleast one of: shooting different types/classes of solder pastes;shooting droplets with different shot sizes/ranges; and shootingdroplets of various types of viscous media (e.g., a first jetting headassembly may be configured to droplets).

At least one other example embodiment provides a linescan jetting methodfor jetting viscous medium on a workpiece. According to at least thisexample embodiment, the method includes: moving the workpiece in a firstdirection; jetting, by a first jetting head assembly movably fixed to afirst beam, the viscous medium on the workpiece while moving the firstjetting head assembly along the first beam in a second direction, whichis perpendicular to the first direction; and jetting, by a secondjetting head assembly fixed to a second beam, viscous medium on theworkpiece while moving the second jetting head assembly along the secondbeam in the second direction.

According to at least some example embodiments, the workpiece may moveincrementally through the linescan jetting apparatus. The first andsecond jetting head assemblies may jet viscous medium on the workpieceat least one of concurrently and simultaneously. The method may furtherinclude: moving the first and second jetting head assemblies in a thirddirection, which is perpendicular to the first and second directions.

According to at least some example embodiments, the jetting by the firstand second jetting head assemblies may include at least one of: shootingdifferent types/classes of solder pastes; shooting droplets withdifferent shot sizes/ranges; and shooting droplets of various types ofviscous media.

At least one other example embodiment provides a linescan jetting methodfor jetting viscous medium on a workpiece. According to at least thisexample embodiment, the method includes: moving the workpiece in a firstdirection and in a step-wise movement forward; and jetting, by a jettinghead assembly movably fixed to a beam, the viscous medium on theworkpiece while moving along the beam in a second direction, which isperpendicular to the first direction.

BRIEF DESCRIPTION OF DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a perspective view showing a general outline of a conventionalmachine to apply viscous medium including a system for jetting;

FIG. 2 is a schematic view of an example embodiment of a docking deviceand a jetting head assembly;

FIG. 3 is a schematic view showing the underside of the jetting headassembly shown in FIG. 2;

FIG. 4 is a schematic view showing a cut away portion of the jettinghead assembly shown in FIG. 2;

FIGS. 5A-5C illustrate different example degrees of viscous mediumfilling a nozzle space;

FIGS. 6A and 6B illustrate operation principles of a jetting headassembly;

FIG. 7 is a schematic view of an example nozzle;

FIG. 8A is a schematic plan view illustrating an example embodiment of abi-axial jetting apparatus for depositing and/or jetting viscous mediumon a workpiece;

FIG. 8B is a front perspective view of the bi-axial jetting apparatusshown in FIG. 8A;

FIG. 9A is a schematic plan view illustrating an example embodiment of auni-axial jetting apparatus for depositing and/or jetting viscous mediumon a workpiece;

FIG. 9B is a front perspective view of the uni-axial jetting apparatusshown in FIG. 9A;

FIG. 10 illustrates an example embodiment of an apparatus for depositingand/or jetting viscous medium on moving workpieces;

FIG. 11A is a schematic plan view of a linescan depositing/jettingapparatus according to an example embodiment;

FIG. 11B is a front perspective view of the linescan depositing/jettingapparatus shown in FIG. 11A; and

FIG. 12 illustrates an example of optical linescan methodology.

DETAILED DESCRIPTION

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a”, “an” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on”, “engaged to”,“connected to” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto”, “directly connected to” or “directly coupled to” another element orlayer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”,“lower”, “above”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

Specific details are provided in the following description to provide athorough understanding of example embodiments. However, it will beunderstood by one of ordinary skill in the art that example embodimentsmay be practiced without these specific details. For example, systemsmay be shown in block diagrams so as not to obscure the exampleembodiments in unnecessary detail. In other instances, well-knownprocesses, structures and techniques may be shown without unnecessarydetail in order to avoid obscuring example embodiments.

In the context of the present application, it is to be noted that theterm “viscous medium” should be understood as highly viscous medium witha viscosity (e.g., dynamic viscosity) typically about or above 1 Pa s(e.g., solder paste, solder flux, adhesive, conductive adhesive, or anyother kind of medium of fluid used for fastening components on asubstrate, conductive ink, resistive paste, or the like, all typicallywith a viscosity about or above 1 Pa s). The term “jetted droplet”, or“shot” should be understood as the volume of the viscous medium that isforced through the jetting nozzle and moving towards the substrate inresponse to an impact of the impacting device.

In the context of the present application, it is noted that the term“jetting” should be interpreted as a non-contact deposition process thatutilizes a fluid jet to form and shoot droplets of a viscous medium froma jetting nozzle onto a substrate, as compared to a contact dispensingprocess, such as “fluid wetting”. In contrast to a dispenser anddispensing process where a needle in combination with, for contactdispensing, the gravitation force and adhesion force with respect to thesurface is used to dispense viscous medium on a surface, an ejector orjetting head assembly for jetting or shooting viscous medium should beinterpreted as an apparatus including an impacting device, such as animpacting device including, for example, a piezoelectric actuator and aplunger, for rapidly building up pressure in a fluid chamber by therapid movement (e.g., rapid controlled mechanical movement) of animpacting device (e.g., the rapid movement of a plunger) over a periodof time that is more than about 1 microseconds, but less than about 50microseconds, thereby providing a deformation of the fluid in thechamber that forces droplets of viscous medium through a jetting nozzle.In one implementation, an ejection control unit applies a drive voltageintermittently to a piezoelectric actuator, thereby causing anintermittent extension thereof, and a reciprocating movement of aplunger with respect to the assembly housing of the ejector or jettingassembly head.

“Jetting” of viscous medium should be interpreted as a process forejecting or shooting droplets of viscous medium where the jetting ofdroplets of the viscous medium onto a surface is performed while the atleast one jetting nozzle is in motion without stopping at each locationon the workpiece where viscous medium is to be deposited. Jetting ofviscous medium should be interpreted as a process for ejecting orshooting droplets of viscous medium where the ejection of a dropletthrough a nozzle is controlled by an impacting device building up arapid pressure impulse in a fluid chamber over a time period thattypically is more than about 1 microseconds and less than about 50microseconds. For the movement of the impacting device to be rapidenough to build up a pressure impulse in the fluid chamber to forceindividual droplets or shots of the relatively highly viscous fluids(with a viscosity of about or above 1 Pa s) out of the chamber throughthe jetting nozzle, the break-off is induced by the impulse of the shotitself and not by gravity or the movement of a needle in an oppositedirection. A volume of each individual droplet to be jetted onto theworkpiece may be between about 100 pL and about 30 nL. A dot diameterfor each individual droplet may be between about 0.1 mm and about 1.0mm. The speed of the jetting, i.e. the speed of each individual droplet,may be between about 5 m/s and about 50 m/s. The speed of the jettingmechanism, e.g. the impacting mechanism for impacting the jettingnozzle, may be as high as between about 5 m/s and about 50 m/s but istypically smaller than the speed of the jetting, e.g. between about 1m/s and about 30 m/s, and depends on the transfer of momentum throughthe nozzle.

The terms “jetting” and “jetting head assembly” in this disclosure andthe claims, refer to the break-off of a fluid filament induced by themotion of the fluid element in contrast to a slower natural break-offakin to dripping where the a break-off of a fluid filament is driven forexample by gravity or capillary forces.

In order to distinguish “jetting” of droplets of a viscous medium usinga “jetting head assembly” such as an ejector-based non-contact jettingtechnology from the slower natural dripping break-off driven by gravityor capillary forces, we introduce below non-dimensional numbers thatdescribe a threshold for the dripping-jetting transition for filamentbreak-off for different cases and fluids that are driven by differentphysical mechanisms.

For elastic fluids, the terms “jetting” and “jetting head assembly”refer to the definition of jetting droplets by reference to theWeissenberg number, Wi=λU_(jet)/R, where λ is the dominant relaxationtime of the fluid, U_(jet) is the speed of the fluid and R is the radiusof the jet, can be used and the threshold for dripping-jetting isapproximately 20<Wi_(th)<40.

For fluids where break-off is controlled by viscous thinning, the terms“jetting” and “jetting head assembly” refer to the definition of jettingdroplets by reference to the Capillary number, described byCa=η₀U_(jet)/γ, where η₀ is the yield viscosity and γ is the surfacetension, can be used to introduce a threshold for dripping-jetting ofCa_(th)≈10.

For fluids where break-off is dominated by inertial dynamics, the terms“jetting” and “jetting head assembly” refer to the definition of jettingdroplets by reference to the Weber number, expressed as ρU²jetR/γ, whereρ is the fluid density, can be used to introduce a jetting-drippingthreshold of We_(th)≈1.

The ability to eject a more precise and/or accurate volume of viscousmedium from a given distance at a specific position on a workpiece whilein motion are hallmarks of viscous jetting. These characteristics allowthe application of relatively highly viscous fluids (e.g., above 1 Pa s)while compensating for a considerable height variation on the workpiece(h=about 0.4 to about 4 mm). The volumes are relatively large comparedto ink jet technology (between about 100 pL and about 30 nL) as are theviscosities (viscosities of about or above 1 Pa s).

At least some example implementations of the technology disclosedprovide increased speed of application due to the jetting “on the fly”principle of ejector-based jetting technology applying viscous mediumwithout stopping for each location on the workpiece where viscous mediumis to be deposited. Hence, the ability of ejector-based jettingtechnology of jetting droplets of the viscous medium onto a first(horizontal) surface is performed while the at least one jetting nozzleis in motion without stopping at each location provides an advantage interms of time savings over capillary needle dispensing technology.

Typically, an ejector is software controlled. The software needsinstructions for how to apply the viscous medium to a specific substrateor according to a given (or alternatively, desired or predetermined)jetting schedule or jetting process. These instructions are called a“jetting program”. Thus, the jetting program supports the process ofjetting droplets of viscous medium onto the substrate, which processalso may be referred to as “jetting process” or “printing process”. Thejetting program may be generated by a pre-processing step performedoff-line, prior to the jetting process.

As discussed above, the term “viscous medium” may be solder paste, flux,adhesive, conductive adhesive, glue or any other kind of medium used forfastening components on a workpiece, substrate, conductive ink,resistive paste, or the like. However, example embodiments should not belimited to only these examples. As discussed herein, the term “deposit”refers to an amount of viscous medium applied at a position on aworkpiece as a result of one or more jetted droplets (also referred toas shots).

For at least some solder paste applications, the solder paste mayinclude between about 40% and about 60%, inclusive, by volume of solderballs and the rest of the volume is solder flux. The solder balls aretypically about 20 microns in diameter, or between about 10 and about 30microns, inclusive, in diameter.

In at least some solder paste applications, the volume percent of solderballs of average size may be in the range of between about 5% and about40%, inclusive, of the entire volume of solid phase material within thesolder paste. In other applications, the average diameter of the firstfraction of solder balls may be within the range of between about 2 andabout 5 microns, inclusive, while the average diameter of a secondfraction of solder balls may be between about 10 and about 30 microns,inclusive.

As discussed herein, the term “deposit size” refers to the area on theworkpiece, such as a substrate, that a deposit will cover. An increasein the droplet volume generally results in an increase in the depositheight as well as the deposit size.

A “workpiece” may be a board (e.g., a printed circuit board (PCB) orflexible PCB), a substrate for ball grid arrays (BGA), a flexiblesubstrate (e.g., paper) chip scale packages (CSP), quad flat packages(QFP), wafers, flip-chips, or the like.

As discussed herein, movement is discussed in terms of the x-, y-, andz-directions. It should be understood, however, that movement in each ofthese directions may also be referred to as movement in the x-, y- orz-dimension, respectively. Thus, if a component moves in each of the x-,y- and z-directions, that component may be said to move threedimensionally or in three dimensions.

Bi-Axial Jetting Example Embodiment

At least one example embodiment provides a bi-axial jetting apparatusand method for depositing/jetting viscous medium on a workpiece. Atleast this example embodiment provides a bi-axial mechanical solutionfor multiple depositing heads where at least one of the depositing headsis a jetting head. In one implementation, at least one of the multipledepositing heads may be a dispensing head.

The bi-axial jetting apparatus and method may increase production speedwhen jetting viscous medium on a workpiece held at a fixed position withrespect to the movement of the jetting heads. The increase in jettingspeed for the multiple head configuration is obtained through amulti-beam gantry where each depositing head moves independently on adedicated beam, and each beam is configured to move independently in adirection perpendicular to the direction of movement of the depositingheads.

In this example, the depositing head assemblies are configured to moveconcurrently and/or simultaneously in three dimensions.

FIG. 8A is a schematic plan view illustrating an example embodiment of abi-axial jetting apparatus for depositing/jetting viscous medium on aworkpiece. FIG. 8B is a front perspective view of the bi-axial jettingapparatus shown in FIG. 8A.

Referring to FIGS. 8A and 8B, the bi-axial jetting apparatus includes aplatform 1002 configured to hold a workpiece W. A frame FR is arrangedabove the platform 1002. The frame FR includes at least two independentgantry beams 1006A and 1006B arranged in parallel with one another andlongitudinally in the x-direction. A first depositing head assembly1004A is arranged on the first gantry beam 1006A, and a seconddepositing head assembly 1004B is arranged on the second gantry beam1006B to enable more efficient depositing of viscous medium on theworkpiece W. Each depositing head assembly 1004A and 1004B is configuredto deposit the same or different viscous medium on the workpiece W. Anexample depositing head assembly will be discussed in more detail below.According to at least some example embodiments, the depositing headassemblies 1004A and 1004B are configured to concurrently and/orsimultaneously deposit viscous medium on the workpiece W.

The first and second gantry beams 1006A and 1006B are reciprocally andmovably connected between opposite sides of the frame FR, which isrigidly fixed in (or as part of) the bi-axial jetting apparatus. Thefirst and second gantry beams 1006A and 1006B may be connected to theframe FR using bearings or the like so as to enable the first and secondgantry beams 1006A and 1006B to slide along the frame FR in they-direction, which is perpendicular to the x-direction. Movement of thefirst and second gantry beams 1006A and 1006B may be driven by linearmotors (not shown), which are well-known in the art.

The depositing head assemblies 1004A and 1004B are movably connected torespective ones of the gantry beams 1006A and 1006B such that thedepositing head assemblies 1004A and 1004B are movable in thex-direction along the respective gantry beams 1006A and 1006B. Movementof the depositing head assemblies 1004A and 1004B may be driven bylinear motors (not shown). In this example, the direction of movement ofthe gantry beams 1006A and 1006B is perpendicular or substantiallyperpendicular to the direction of movement of the depositing headassemblies 1004A and 1004B.

Control of the gantry beams 1006A and 1006B is coordinated to preventcollisions between the gantry beams 1006A and 1006B and the depositinghead assemblies 1004A and 1004B. The coordinated motion of the gantrybeams 1006A and 1006B and the depositing head assemblies 1004A and1004B, together with a linear motion ability of the depositing headassemblies 1004A and 1004B in the z-direction, enables depositing headsto move (e.g., simultaneously and/or concurrently) in three-dimensionalspace, while depositing viscous medium on the workpiece W.

The coordinated motion of the depositing head assemblies 1004A and 1004Balso allows for feed-back based jetting/depositing strategies and/ormethods in which unacceptable variations in volume of viscous mediumdeposited by one depositing head may be reactively repaired by anotherdepositing head. This may suppress and/or eliminate the need for anadditional inspection step. In this regard, a real-time reconfigurationof the depositing path for at least one of the depositing heads may beutilized.

The bi-axial jetting apparatus shown in FIGS. 8A and 8B is configuredsuch that the depositing head assemblies 1004A and 1004B are able todeposit viscous medium on any portion of the workpiece W; that is, thedepositing head assemblies 1004A and 1004B are configured to depositviscous medium on the entire surface of the workpiece W. In someembodiments of the implementation shown in FIGS. 8A and 8B, one of thedepositing head assemblies 1004A and 1004B is a jetting head assemblyshooting droplets of viscous medium and the other depositing headassembly is a dispenser assembly configured to perform capillary needledispensing of viscous medium (e.g., glue) on the workpiece.

The depositing head assemblies 1004A and 1004B may be configured to:shoot different types/classes of solder pastes; shoot droplets withdifferent shot sizes/ranges (e.g., overlapping or non-overlappingranges); and/or shoot droplets of various types of viscous media (solderpaste, glue, etc.). Additionally, the depositing head assemblies 1004Aand/or 1004B may be used for add-on depositing, jetting and/or repair asdesired.

According to at least some example embodiments, at least one of the atleast two depositing head assemblies 1004A and 1004B may be a dispensinghead (e.g., for dispensing glue) and at least one other of the at leasttwo jetting head assemblies 1004A and 1004B may be an ejector basedjetting head assembly for shooting solder paste. Example depositvolumes, shot sizes, and types of viscous medium for the jetting anddispensing are shown below in Table 1. Although some examples shown inTable 1 are discussed with regard to implementations of the technologydisclosed using a dispensing head together with the at least one jettinghead configured to shoot droplets of viscous medium, according to otherimplementations of the technology disclosed both heads are jettingheads.

TABLE 1 Jetting/ Type of Viscous Shot/dot Deposit Volume DispensingMedium Size (approx. nL) a) Jetting Solder paste Small  1-5 nL JettingSolder paste Regular  5-15 nL b) Jetting Solder paste Regular  5-15 nLJetting Solder paste Large 15-50 nL c) Jetting Solder paste Regular 5-15 nL Dispensing Adhesive Regular  5-20 nL d) Jetting Solder pasteRegular  5-15 nL Jetting Conductive adhesive Regular  5-20 nL e) JettingAdhesive Regular  5-20 nL Dispensing Conductive adhesive Regular  5-20nL f) Jetting Solder paste Regular  5-15 nL Dispensing Underfill Regular10-50 nL

The diameters of the shot/dot size depend on the form of the deposit. Inone example, however, an approximate diameter for deposit volume ofabout 1 nL is between about 120 μm and 150 μm; an approximate diameterfor deposit volume of about 5 nL is between about 250 μm and about 350μm; an approximate diameter for deposit volume of about 15 nL is betweenabout 450 μm and about 550 μm; and an approximate diameter for depositvolume of about 50 nL is between about 600 μm and about 700 μm.

If at least two (ejector-based) jetting head assemblies are used toshoot viscous medium with different shot sizes, the shot sizes for theat least two jetting heads may be in the range of about 1-50 nLdepending on the viscous medium to be jetted.

If at least two (ejector-based) jetting head assemblies are used toshoot different types of viscous medium, it may be advantageous to shootsolder paste with one of the jetting head assemblies and adhesive,conductive adhesive/glue or underfill with the other jetting headassembly because the current surface mount process may benefit from amodule adapted to either mixed production, alternative board modalities,repair applications, etc.

Although only two depositing head assemblies 1004A and 1004B and twogantry beams 1006A and 1006B are shown in FIGS. 8A and 8B, exampleembodiments should not be limited to this example. Rather, exampleembodiments may include additional depositing head assemblies mounted onthe gantry beams 1006A and/or 1006B and/or additional gantry beamsincluding additional depositing head assemblies.

Depositing Head Assembly

FIGS. 2 and 3 illustrate an example embodiment of a depositing headassembly (e.g., 1004A, 1004B) discussed above with regard to FIGS. 8Aand 8B. Although the example shown in FIGS. 2 and 3 will be discussedwith regard to depositing head assembly 1004A, it should be understoodthat the both depositing head assemblies 1004A and 1004B may be jettinghead assemblies and that depositing head assembly 1004B may be the sameor substantially the same as the depositing head assembly 1004A. In atleast some example embodiments of the implementation shown in FIGS. 2and 3, one of the depositing head assemblies 1004A and 10004B is ajetting head assembly shooting droplets of viscous medium and the otherdepositing head assembly is a dispenser assembly configured to performdispensing of viscous medium on the workpiece.

Referring to FIGS. 2 and 3, the depositing head assembly 1004A includesan assembly holder 11, which is configured to connect the depositinghead assembly 1004A to an assembly support 10 of a docking device 8. Thedepositing head assembly 1004A further includes an assembly housing 15and a supply container 12 to provide a supply of viscous medium.

The depositing head assembly 1004A is connected to a vacuum ejector, anda source of pressurized air via a pneumatic interface having inlets 42positioned to interface in airtight engagement with a complementarypneumatic interface having outlets 41 of the docking device 8. Theoutlets 41 are connected to inlet nipples 9 via internal conduits of thedocking device 8.

The depositing head assembly 1004A may be configured to: shoot differenttypes/classes of solder pastes; shoot droplets with different shotsizes/ranges (e.g., overlapping or non-overlapping ranges) and/or shootdroplets of various types of viscous media (solder paste, glue, etc.).Additionally, the depositing head assembly 1004A may be used for add-onjetting and/or repair.

FIG. 4 illustrates example contents and function of parts enclosed inthe assembly housing 15 in more detail.

Referring to FIG. 4, the depositing head assembly 1004A includes animpacting device. In this example, the impacting device includes apiezoelectric actuator 21 having a number of relatively thin,piezoelectric elements stacked together to form an actuator part 21 a.An upper end of the actuator part 21 a is rigidly connected to theassembly housing 15. The depositing head assembly 1004A further includesa bushing 25 rigidly connected to the assembly housing 15. The impactingdevice further includes a plunger 21 b, which is rigidly connected to alower end of the actuator part 21 a. The plunger 21 b is axially movablewhile slidably extending through a piston bore 35 in the bushing 25. Cupsprings 24 are provided to resiliently balance the plunger 21 b againstthe assembly housing 15, and to provide a preload for the actuator part21 a. An ejection control unit (not shown) applies a drive voltageintermittently to the piezoelectric actuator 21, thereby causing anintermittent extension thereof, and hence a reciprocating movement ofthe plunger 21 b with respect to the assembly housing 15, in accordancewith pattern printing data.

An impact end surface 38 of the piston portion of the plunger 21 b isarranged relatively close to the nozzle 26. A jetting chamber 37 isdefined by the end surface 38 of the plunger 21 b, the cylindrical innerwall of the nozzle 26, the upper surface 92 (FIG. 7) of the nozzle 26and the upper portion 96 (FIG. 7) of the nozzle space 28. Thus, thejetting chamber 37 is connected to the upper portion of the nozzle space28. Axial movement of the plunger 21 b towards the nozzle 26 caused bythe intermittent extension of the piezoelectric actuator 21 may resultin a decrease (e.g., relatively rapid decrease) in the volume of thejetting chamber 37, and thus pressurization (e.g., a rapidpressurization) and jetting of the viscous medium in the nozzle space 28through the nozzle outlet 27.

Solder paste is supplied to the jetting chamber 37 from the supplycontainer 12 (FIG. 3) via a feeder 23. The feeder 23 includes anelectric motor (not shown) having a motor shaft 29 partly provided in atubular bore 30, which extends through the assembly housing 15 to anoutlet port 36. The outlet port 36 communicates with the jetting chamber37 via a tubular bore 31 provided in the housing 15, and an annularspace formed between the piston portion of the plunger 21 b and acylindrical inner wall provided by the piston bore 35 and the uppercylindrical inner wall 40 of the nozzle 26, respectively. The annularspace extends from the outlet of the tubular bore 31 down to the jettingchamber 37.

An end portion of the motor shaft 29 forms a rotatable feed screw 32which is provided in, and coaxial with, the tubular bore 30, and whichends at the outlet port 36. An essential portion of the rotatable feedscrew 32 is surrounded by a tube 33, made of an elastomer or the like,arranged coaxially therewith in the tubular bore 30. Threads of therotatable feed screw 32 make sliding contact with the innermost surfaceof the tube 33. An example of an alternative to the tube is an array ofresilient, elastomeric O-rings.

The depositing head assembly 1004A further includes a plate shaped orsubstantially plate shaped jetting nozzle 26 operatively directedagainst the workpiece, onto which small droplets of viscous medium areto be jetted. A through hole is formed through the jetting nozzle 26.

FIG. 7 illustrates an example implementation of the technology disclosedof the nozzle 26 in more detail.

Referring to FIG. 7, the through hole is defined by a firstfrustro-conical portion 91, extending from a top surface 92 of thenozzle 26 downwards through a portion of (e.g., most of) the thicknessof the nozzle 26, and a second frustro-conical portion 93 extendingupwards from a bottom surface 94 of the nozzle 26 to the plane of thetop of the first frustro-conical portion 91. Thus, the tops of thefrustro-conical portions 91, 93 are directed towards (or face) eachother. The diameter of the top of the second frustro-conical portion 93is larger than the diameter of the top of the first frustro-conicalportion 91. The first and second frustro-conical portions 91, 93 areconnected by a ring portion 95, which is in parallel with the top andbottom surfaces 92, 94 of the nozzle 26. The top of the firstfrustro-conical portion 91 defines a nozzle outlet 27 through which thedroplets of viscous medium are jetted onto the workpiece. Furthermore, anozzle space 28 is defined by the inner walls of the firstfrustro-conical portion 91. Thus, the nozzle outlet 27 is located at thering portion 95 of the nozzle 26.

The upper portion 96 of the nozzle 26 (the base of the firstfrustro-conical portion 91) is arranged for receiving viscous medium,which is forced through the nozzle space 28 and out of the nozzle outlet27.

Returning to FIG. 4, a plate or wall 14 (also shown in FIG. 3) isarranged below, or downstream, of the nozzle outlet 27, as seen in thejetting direction. The plate 14 is provided with a through hole 13,through which the jetted droplets pass without being hindered ornegatively affected by the plate 14. Consequently, the hole 13 isconcentric with the nozzle outlet 27. The plate 14 is spaced apart fromthe nozzle outlet 27. Between the plate 14 and the nozzle outlet 27, anair flow chamber 44 is formed. The chamber 44 is a space acting as achannel or guide that is connected with a vacuum ejector for generatingan air flow as illustrated, for example, by the arrows of FIG. 7, at andpast the nozzle outlet 27. In this example, the air flow chamber 44 isdisc shaped, and the hole 13 acts as an inlet for the air flow towardsand past the nozzle outlet 27.

The degree of filling of the nozzle space 28 before each jetting is setin order to obtain a controlled and individually adjusted amount ofviscous medium in each droplet.

Example degrees of filling (e.g., ‘a’, ‘b’, and ‘c’) are shown in FIGS.5A-5C, which illustrate an alternative configuration of the nozzle 60.The nozzle 60 still includes a frustro-conical portion 61 that defines aportion of the nozzle space 62. However, rather than the secondfrustro-conical portion 93, the nozzle 60 includes a cylindrical portion63. The upper end of the cylindrical portion 63 coincides with the topend of the frustrum of a conical portion 61, and the lower end of thecylindrical portion 63 is positioned at the bottom surface 65 of thenozzle 60. In this alternative example, the nozzle outlet 64 is definedby the lower end of the cylindrical portion 63.

As seen from FIGS. 5A-5C, the nozzle space 62 is filled from the upperportion thereof towards the nozzle outlet 64. Thus, if the nozzle space62 is filled to a relatively small extent, as shown in FIG. 5A, acomparatively small droplet is jetted, whereas if the nozzle space isfilled or substantially filled, as in FIG. 5C, a larger droplet isjetted.

As shown in FIGS. 6A and 6B, before jetting a first droplet after apause, or at start-up of the jetting machine, the accuracy of the degreeof filling of the nozzle space, in these figures denoted 72, isascertained. This may be obtained by feeding viscous medium into thenozzle space 72 via the feed screw 32 (shown in FIG. 4) such that theviscous medium fills or substantially fills the nozzle space 72, asshown in FIG. 6A. In this process, relatively small amounts of viscousmedium may be forced out of the nozzle outlet 74. Thanks to the suctionfunction obtained by air flow, excessive viscous medium is supressedand/or prevented from falling onto a board located beneath the nozzle70. The air flow is schematically indicated by the horizontal arrows inFIG. 6A. It is noted that for ease of description, the plate downstreamof the nozzle outlet has been omitted from FIGS. 6A and 6B, as well asin FIGS. 5A-5C. During this process, the plunger 21 b is held in an idleposition.

Returning to FIG. 4, the volume of the jetting chamber is increased byretracting the plunger 21 b. The plunger 21 b is retracted bycontrolling the actuator part 21 a. The plunger 21 b is retracted tomove the end surface a given, desired or predetermined distance so as toempty the nozzle space 28/72 to an accurately given, desired orpredetermined extent. In the example shown in FIG. 6B, the nozzle space72 has been substantially emptied of viscous medium. Having now obtainedthe appropriate degree of filling of the nozzle space 28/72, the jettingdevice is ready for impacting. Droplets may then be jetted essentiallyimmediately to ensure that there is little or no time for substantivechanges in the jetting conditions to occur.

The jetting sequence then begins by feeding viscous medium into thenozzle space 28 in accordance with information on what size of dropletthat is to be jetted. When the feeding is complete, the actuator 21 isenergized to obtain an impacting movement of the plunger 21 b. Theimpacting movement of the plunger 21 b rapidly decreases the volume ofthe jetting chamber 37 to such an extent that the amount of viscousmedium that is present in the nozzle space 28 is jetted out of thenozzle outlet 27 and onto the workpiece.

Uni-Axial Jetting Example Embodiment

At least one other example embodiment provides a uni-axial jettingapparatus and method to deposit and/or jet viscous medium on aworkpiece. In at least this example embodiment, multiple depositing headassemblies are attached to a single gantry beam. The depositing headassemblies are configured to move vertically as well as independentlyalong the gantry beam. The gantry beam is configured to move in adirection perpendicular to the directions of movement of the depositinghead assemblies. In this example embodiment, the depositing headassemblies are movable together in one direction (e.g. the y-direction)and independently in two other directions (e.g., the x-direction and thez-direction), which are perpendicular to the first direction. In thisexample, the depositing head assemblies are configured to moveconcurrently and/or simultaneously in three dimensions. In one example,at least one of the depositing head assemblies may be a dispensing headassembly.

Uni-axial jetting apparatuses and methods according at least someexample embodiments may increase jetting speed by having multiple (e.g.,two) depositing heads deposit/jet viscous medium on a workpiececoncurrently and/or simultaneously. According to at least this exampleembodiment, multiple (e.g., two) different types of depositing heads maybe used to remove the need to exchange depositing heads duringproduction.

FIG. 9A is a schematic plan view illustrating an example embodiment of auni-axial jetting apparatus for depositing and/or jetting viscous mediumon a workpiece. FIG. 9B is a front perspective view of the uni-axialjetting apparatus shown in FIG. 9A.

Referring to FIGS. 9A and 9B, the uni-axial jetting apparatus includes aplatform 2002 configured to hold a workpiece W. A frame FR2 is arrangedabove the platform 2002 such that the workpiece W is held below thegantry beam 2006 and depositing head assemblies 2004A and 2004B. Theuni-axial jetting apparatus is configured such that the depositing headassemblies 2004A and 2004B are able to deposit viscous medium on anyportion of the workpiece W; that is, the depositing head assemblies2004A and 2004B are configured to deposit viscous medium on the entiresurface of the workpiece W.

The single gantry beam 2006 is reciprocally and movably fixed toopposite ends of the frame FR2 in the same or substantially the samemanner as the gantry beams 1006A and 1006B discussed above with regardto FIGS. 8A and 8B. At least two depositing head assemblies 2004A and2004B are reciprocally and movably fixed to the gantry beam 2006. The atleast two depositing head assemblies 2004A and 2004B are fixed to thegantry beam 2006 in the same or substantially the same manner as thedepositing head assemblies 1004A and 1004B discussed above with regardto FIGS. 8A and 8B. The at least two depositing head assemblies 2004Aand 2004B are configured to move longitudinally along the gantry beam2006.

Each of the depositing head assemblies 2004A and 2004B is configured todeposit the same or different viscous medium on a surface of theworkpiece W extending in the x-y dimension. In one example, eachdepositing head assembly 2004A and 2004B may be the same orsubstantially the same as the depositing head assembly 1004A discussedabove. According to at least this example embodiment, the depositinghead assemblies 2004A and 2004B are configured to concurrently and/orsimultaneously deposit viscous medium on the workpiece W, but arecontrolled independently of each other.

The gantry beam 2006 is configured to slide along the frame FR2 in they-direction, and the depositing head assemblies 2004A and 2004B areconfigured to move independent of each other in the x and z directions.The movement of the depositing head assemblies 2004A and 2004B arecoordinated so that the depositing head assemblies 2004A and 2004B donot collide.

The depositing head assemblies 2004A and 2004B may be configured to:shoot different types/classes of solder pastes; shoot droplets withdifferent shot sizes/ranges (e.g., overlapping or non-overlappingranges); and/or shoot droplets of various types of viscous media (solderpaste, glue, etc.). Additionally, the depositing head assemblies 2004Aand/or 2004B may be used for add-on depositing, jetting and/or repair asdesired.

According to at least some example embodiments, at least one of the atleast two depositing head assemblies 2004A and 2004B may be a dispensinghead (e.g., for dispensing glue) and at least one other of the at leasttwo depositing head assemblies 2004A and 2004B may be an ejector basedjetting head assembly for shooting solder paste. Example depositvolumes, shot sizes, and types of viscous medium for the jetting anddispensing are shown above in Table 1.

As with the example embodiment shown in FIGS. 8A and 8B, if at least two(ejector-based) jetting head assemblies are used to shoot viscous mediumwith different shot sizes, the shot sizes for the at least two jettingheads may be in the range of about 1-50 nL depending on the viscousmedium to be jetted.

If at least two (ejector-based) jetting head assemblies are used toshoot different types of viscous medium, it may be advantageous to shootsolder paste with one of the jetting head assemblies and adhesive,conductive adhesive or underfill with the other jetting head assemblybecause the current surface mount process may benefit from a moduleadapted for mixed production, alternative board modalities, repairapplications, etc.

Although only two depositing head assemblies 2004A and 2004B are shownin FIGS. 9A and 9B, example embodiments should not be limited to thisexample. Rather, example embodiments may include additional depositinghead assemblies mounted on the gantry beam 2006 and movable in the x andz-directions.

Jetting Viscous Medium on Moving Workpiece

Example embodiments also provide methods and apparatuses for depositingand/or jetting viscous medium on a moving workpiece (e.g., a flexiblesubstrate or the like).

According to at least some example embodiments, viscous medium may bedeposited and/or jetted on a moving workpiece (e.g., flexible substrateor the like), for example, while compensating for workpiece topologyand/or stretching.

At least some example embodiments may provide increased throughput forrelatively simple and/or relatively high volume products requiringmounted components (e.g., relatively high throughput products producedon rolls, hybrid products with relatively few components produced involume, etc.).

At least some example embodiments may also provide the ability tocompensate for movement of the workpiece on the fly during jettingand/or depositing of viscous medium.

FIG. 10 illustrates an example embodiment of an apparatus and method fordepositing and/or jetting viscous medium on a moving workpiece. Forexample purposes, the example embodiment shown in FIG. 10 will bedescribed with regard to a flexible substrate.

Referring to FIG. 10, the apparatus includes a first and a secondsupporting arrangement (e.g., cylindrical rollers) 3004A and 3004B. Inthe example shown in FIG. 10, the supporting arrangements 3004A and3004B are cylindrical rollers, and will be discussed as such. However,example embodiments should not be limited to only this implementation.

The first and second cylindrical rollers 3004A and 3004B are configuredto hold a flexible substrate 3002. The cylindrical rollers 3004A and3004B may be driven by a linear motor (not shown) to move the flexiblesubstrate 3002 in the y-direction from the first cylindrical roller3004A to the second cylindrical roller 3004B.

To speed up the depositing and/or jetting of viscous medium on theflexible substrate, the flexible substrate 3002 maintains continuousmotion while a depositing head assembly 3006 compensates for the motionof the flexible substrate 3002 by moving in the x- and y-directionsduring jetting. The depositing head assembly 3006 may also move in the zdirection as discussed above.

In at least this example embodiment, the flexible substrate 3002 and thedepositing head assembly 3006 move concurrently and/or simultaneouslywhile the depositing head assembly 3006 deposits/jets viscous medium onthe surface of the flexible substrate 3002. The depositing head assembly3006 may be the same or substantially the same as the depositing headassembly 1004A discussed above. Thus, a detailed discussion of thedepositing head assembly 3006 is omitted. Moreover, the depositing headassembly 3006 may be moved in any well-known manner, including thatdiscussed herein with regard to other example embodiments.

According to at least the example embodiment shown in FIG. 10, theflexible substrate 3002 need not be stopped and/or secured to identifythe fiducials 3010, and thereafter deposit a viscous medium (e.g.,solder paste, conformal filler, conductive adhesives, etc.) on theflexible substrate 3002.

The intrinsic behavior of moving flexible substrates, which includeselastic properties and relatively small changes in lateral positioning,may require a repetitive calibration procedure to control the movementof the depositing head assembly 3006 in the plane of the moving flexiblesubstrate 3002. The calibration procedure may be based on the movementof the fiducials 3010, which may be part of the jetting pattern ordedicated patterns for calibration purposes.

The correct placement of the deposit of viscous medium on the flexiblesubstrate 3002 may be calculated using ballistic algorithms that takeinto account the relative speeds of the moving flexible substrate 3002and the depositing head assembly 3006. The calibration procedure mayalso include a height calibration procedure, either optical ormechanical, to ensure the movement of the depositing head assembly 3006in the vertical z-direction while in motion over the flexible substrate3002.

Still referring to the example embodiment shown in FIG. 10, acompensatory algorithm may be used to measure the speed of thedepositing head assembly 3006 relative to the moving flexible substrate3002, for example, by using pads on the flexible substrate 3002 asdiscrete reference marks to enable more accurate deposition of viscousmedium on the flexible substrate 3002.

Still referring to FIG. 10, the depositing head assembly 3006 may beconfigured to: shoot different types/classes of solder pastes; shootdroplets with different shot sizes/ranges (e.g., overlapping ornon-overlapping ranges); and/or shoot droplets of various types ofviscous media (e.g., solder paste, glue, etc.). Additionally, thedepositing head assembly 3006 may be used for add-on depositing, jettingand/or repair as desired.

According to at least some example embodiments, the depositing headassembly 3006 may be a dispensing head (e.g., for dispensing glue) or anejector based jetting head assembly for shooting solder paste. Exampledeposit volumes, shot sizes, and types of viscous medium for the jettingand dispensing are shown in Table 1.

In the example embodiment shown in FIG. 10, if more than one(ejector-based) jetting head assembly is used to shoot viscous mediumwith different shot sizes, the shot sizes for the at least two jettingheads may be in the range of about 1-50 nL depending on the viscousmedium to be jetted.

If more than one (ejector-based) jetting head assembly is used to shootdifferent types of viscous medium, it may be advantageous to shootsolder paste with one of the jetting head assemblies and adhesive,conductive adhesive or underfill with the other jetting head assemblybecause the current surface mount process may benefit from a moduleadapted for mixed production, alternative board modalities, repairapplications, etc.

Linescan Jetting Example Embodiment

One or more other example embodiments provide methods and apparatusesfor linescan jetting and/or depositing of viscous medium on a workpieceusing one or more depositing heads. At least this example embodimentutilizes a modular conveyor strategy.

At least this example embodiment enables jetting of workpieces (e.g.,boards) based on a rectilinear strategy. According to at least oneexample embodiment, the rectilinear strategy may be combined withreal-time topology measurements.

According to at least some example embodiments, linescan jetting may beutilized to deposit material on a populated workpiece and/or a workpiecewith previously deposited material (e.g., paste). At least some exampleembodiments may be implemented in a module with a relatively smallfootprint.

According to at least some example embodiments, linescan jetting may beused to address add-on jetting, repair, etc. of populated workpieces.

One or more example embodiments of linescan jetting may also providereal-time compensation for topology measurements.

According to at least some example embodiments, workpieces (e.g.,boards, cards or the like) are moved through a jetting apparatusincrementally and the depositing head is moved in at least two (e.g.,three) dimensions. The movement of the workpiece may also be continuousor incremental and continuous. The movement directions of the depositinghead are normal to the transport direction of the workpiece.

FIG. 11A is a schematic plan view of a linescan jetting apparatusaccording to an example embodiment. FIG. 11B is a front perspective viewof the linescan jetting apparatus shown in FIG. 11A.

Referring to FIGS. 11A and 11B, the linescan jetting apparatus includesa modular conveyor 4002 to carry one or more workpieces W. The conveyor4002 feeds and/or moves the workpiece W through the linescan jettingapparatus incrementally and/or continuously. The incremental and/orcontinuous movement of the workpiece W through the linescan jettingapparatus is controlled according to the resolution of the details to beformed on the workpiece W, such that the movement precision reaches padlimiting specifications.

According to at least some example embodiments, an improved (e.g.,optimal) deposition strategy is proposed for pads present on a printedcircuit board. The allotted deposits allow a certain positioningleniency that may be utilized when applying a ‘travelling salesman’algorithm for the collected deposits, with the movement restriction ofthe line scan motion. The spacing of the allotted deposits and thepositioning requirements on the pad deposits together with thepositioning accuracy of the depositing head determine the x-motion ofthe beam. In one example, a positioning accuracy of 3σ_(ΔX)<50 μm may beused for 0.4 pitch components. In this example, the position of thedeposit with respect to the intended position is better than about 50 μm(3σ_(ΔX)).

Returning to FIGS. 11A and 11B, a frame FR3 is arranged above theconveyor 4002. A first set of beams 4010 are fixed longitudinally in thex-direction to opposite ends of the frame FR3. A second set of beams4004A and 4004B are fixed between the first set of beams 4010longitudinally in the y-direction. The first set of beams 4010 arespaced apart from one another about the length of the beams 4004A and4004B.

A first depositing head assembly 4006A is reciprocally and movably fixedto the beam 4004A, and a second depositing head assembly 4006B isreciprocally and movably fixed to the beam 4004B. The first and seconddepositing head assemblies 4004A and 4004B may be fixed to respectivebeams 4004A and 4004B in the same manner as the depositing headassemblies 1004A and 1004B discussed above with regard to FIGS. 8A and8B.

In the example embodiment shown in FIGS. 11A and 11B, the beams 4010,4004A and 4004B are stationary, and the depositing head assemblies 4006Aand 4006B move along the respective beams 4004A and 4004B in they-direction. The depositing head assemblies 4006A and 4006B also move inthe z-direction as discussed above with regard to other exampleembodiments.

The depositing head assemblies 4006A and 4006B may be the same orsubstantially the same as the depositing head assembly 1004A discussedabove. Thus, a detailed discussion is omitted.

According to at least this example embodiment, the depositing headassemblies 4006A and 4006B move in at most only 2-directions (e.g., yand z) over the workpiece W, for example, while the workpiece W istemporarily at rest. Each of the depositing head assemblies 4006A and4006B travels along a respective beam 4004A and 4004B arrangedperpendicular to the direction of movement of the workpiece W on theconveyor 4002 when the workpiece W moves to a subsequent position.

The depositing head assemblies 4006A and 4006B may be configured to:shoot different types/classes of solder pastes; shoot droplets withdifferent shot sizes/ranges (e.g., overlapping or non-overlappingranges); and/or shoot droplets of various types of viscous media (solderpaste, glue, etc.). Additionally, the depositing head assemblies 4006Aand/or 4006B may be used for add-on depositing, jetting and/or repair asdesired.

According to at least some example embodiments, at least one of thedepositing head assemblies 4006A and 4006B may be a dispensing head(e.g., for dispensing glue) and at least one other of the depositinghead assemblies 4006A and 4006B may be an ejector based jetting headassembly for shooting solder paste. Example deposit volumes, shot sizes,and types of viscous medium for the jetting and dispensing are shownabove in Table 1.

As with the example embodiment shown in FIGS. 8A and 8B, if at least two(ejector-based) jetting head assemblies are used to shoot viscous mediumwith different shot sizes, then the shot sizes for the at least twojetting heads may be in the range of about 1-50 nL depending on theviscous medium to be jetted.

If at least two (ejector-based) jetting head assemblies are used toshoot different types of viscous medium, then it may be advantageous toshoot solder paste with one of the jetting head assemblies and adhesive,conductive adhesive or underfill with the other jetting head assemblybecause the current surface mount process may benefit from a moduleadapted to either mixed production, alternative board modalities, repairapplications, etc.

Example embodiments of methods and apparatuses for line scan jetting ofviscous material on a workpiece provide a basis for a relatively simplemechanical construction in that the movement of the depositing headassemblies is limited to the z-direction and only one of the x- andy-directions, which allows the complementary direction to be reduced.

The incremental movement of the workpiece W by the conveyor 4002 allowstopological re-creation of the surface of the workpiece W via an opticallinescan methodology as the workpiece enters the linescan jettingapparatus. The height information is sampled simultaneously and/orconcurrently as jetting is performed on another part of the workpiece Wand fed back to the control of the z-position of the jetting headassemblies 4006A and 4006B. The incremental topological description ofthe workpiece W is collected and allows for the advance or real-timeplanning of a path over the workpiece W as the workpiece W travels inthe x-direction.

According to at least this example embodiment of the technologydisclosed, the workpiece is moved through the linescan jetting apparatusin a step-wise movement forward in discrete steps. In this example, thesteps of movement of the workpiece forward and the time for a depositinghead to scan the surface of the workpiece in one scan (e.g., in they-direction) while shooting droplets of viscous medium at given, desiredor pre-determined positions/components while in motion may depend on thespecific component footprints on the circuit board and their relativepositioning.

The at least one depositing head may be configured to scan the workpiecein a direction perpendicular to the direction of movement of theworkpiece. The scanning may be conducted in one scan movement for everystep of movement forward of the workpiece. The scan of the surface ofthe workpiece while shooting droplets of viscous medium at given (oralternatively desired or pre-determined) positions/components while inmotion may be conducted after each incremental step forward of theworkpiece, and when the workpiece is not in motion relative to a stagethat holds the workpiece.

The translational steps of the workpiece with respect to the gantry mayrange from centimeters to a minimum step in the range of about 50 μm.The speed to scan the workpiece in the y-direction is related to thespeed of the linear motor, which may be on the order of about 0.5 m/s toabout 1 m/s. In some implementations, the discrete translational stepswhereby the workpiece is step-wise moved forward with respect to thegantry may be adapted to the application and may, for example, be in therange of about 0.1 mm to about 20 mm, inclusive. For example, eachtranslational step may be adapted to correspond to the 0.4 mm pitch of aBGA or a portion of a 0.4 mm pitch of a ball grid array (BGA, e.g.,about 0.2 mm).

FIG. 12 illustrates an example of the optical linescan methodology.

Referring to FIG. 12, a workpiece W travels either continuously ordiscretely in the x-direction along the conveyor 5002. A one-dimensionallaser-based surface topography is measured through the imaging of theresulting laser line from a projected laser plane 5006 from a low-powerlaser source 5004 on the surface of the workpiece W, with or withoutpreviously mounted components, by an imaging camera 5010 at a knownangle α to the laser plane 5006.

The topographical information obtained through the optical linescanmethodology discussed above is collected in a data set related to theposition along the x-direction of the workpiece W, and utilized in thesubsequent depositing action to enable a topographical following of theworkpiece W with the jetting head.

The use of the second depositing head assembly 4006B in the exampleembodiment shown in FIGS. 11A and 11B may enable more dynamically stablemechanical construction if the motion of the depositing head assemblies4006A and 4006B is such that the depositing head assemblies 4006A and4006B move in opposite or counter directions. The first and seconddepositing assemblies 4006A and 4006B may be the same or substantiallythe same in order to decrease the depositing time by about half.Alternatively, the first and second depositing head assemblies 4006A and4006B may be different. In the example shown in FIGS. 11A and 11B, thedepositing head assemblies 4006A and 4006B may include jetting deviceswith different jetting materials to enable more flexible production ofworkpieces. The depositing head assemblies 4006A and 4006B may includejetting heads primed for different jetting volume spans allowing formore effective application of jetting material on the workpiece W.

Still referring to FIGS. 11A and 11B, according to at least one otherexample embodiment, only one of the depositing head assemblies 4006A and4006B may be used for linescan jetting. The workpiece W may be movedinto the depositing/jetting area in the y-direction in the same orsubstantially the same manner as discussed above with regard to FIGS. 8Aand 8B or FIGS. 9A and 9B.

According to at least one other example embodiment, at least one of thedepositing head assemblies in the depositing/jetting apparatuses shownin FIGS. 8A through 9B may be used for linescan jetting. In thisexample, the workpiece W may be moved into the jetting area in they-direction in the same or substantially the same manner as discussedabove with regard to FIGS. 8A and 8B or FIGS. 9A and 9B.

Example embodiments of depositing and/or jetting apparatuses and methodsdiscussed herein may be used in a larger system for depositing/jettingviscous medium (e.g., solder paste or the like). Example embodiments mayincrease production speed and/or yield.

The generation of the jetting program for depositing/jetting viscousmedium using at least two depositing head assemblies involves importing,to a generation program, substrate data relating to a unique given orpredetermined substrate, or a unique given or predetermined set ofidentical or substantially identical substrates; and defining, on basisof the substrate data, where on the substrate the droplets are to bejetted by the at least two depositing head assemblies. In other words,viscous medium may typically be arranged to be jetted onto the substrateaccording to a given, desired or predetermined jetting program.

As an example, a computer program is used for importing and processingcomputer aided design (CAD) data or the like about a substrate. The CADdata may for example comprise data representing position and extensionof contact pads, as well as data representing position, name, and leadsof each individual component that is to be mounted on the substrate. Theprogram can be used to determine where on the substrate the droplets areto be jetted and which depositing head assembly to be used for jettingthat particular droplet, such that each component is provided withdeposits having the required volume, lateral extension, and/or height.This is a process which requires knowledge of the size and volume of asingle droplet, how many droplets that will be sufficient for coveringthe needs of a specific component, and where on the substrate eachdroplet should be placed.

When all droplet configurations for all components have been programmed,a jetting path template may be generated, which describes how thejetting nozzle is going to be moved (e.g., by a jetting machineoperating one or more jetting head assemblies or ejectors) in order tojet the droplets of viscous medium onto the substrate. It is understoodthat the ejectors may operate concurrently or consecutively. The jettingpath template is transferred to the jetting program which is used forrunning the jetting machine, and hence the ejector(s), accordingly. Thejetting program may also comprise jetting parameters (e.g. forcontrolling the feeding of the viscous medium into the nozzle space) andfor controlling the impact of the impacting device, in order to providethe substrate with the required deposits.

The technology disclosed is also advantageous in that it provides thepossibility to correct printing errors by a first ejector or depositinghead assembly by the supplemental jetting of droplets of the viscousmedium by a second ejector or depositing head assembly onto thesubstrate without performing a separate inspection. This implementationmay be based on a realisation that by arranging, for example, a dropletsensor arrangement between the jetting nozzle of a first ejector and thesubstrate, onto which the jetted droplets of viscous media is deposited,the jetting characteristics and the jetted droplets can be monitoredduring the (portion of) a jetting process/program associated with afirst ejector, or depositing head assembly. Information may be obtainedby the jetting machine, and the information may include, for example,information on whether droplets are jetted or not due to an impact ofthe impacting device. Thereby, missed drops may be detected withoutinspection of the surface of the substrate. If a jetted droplet due toan impact of the impacting device is not verified, then the informationmay be used for correction of the deposited volume by, for example,adding supplementary medium to the substrate by a second depositing headassembly where the correction may be performed simultaneously or on thefly, during the present printing process, or in an additional,supplementary printing process. Thereby, the need for time consumingdownstream, posterior inspection of the deposits may be reduced.

The technology disclosed is also advantageous in that it provides thepossibility to, in a supplementary jetting conducted by a secondejector, add viscous medium at a position on a workpiece to the viscousmedium applied by a first ejector. The first ejector may then beconfigured to deposit viscous medium on a surface of a workpiece byshooting droplet volumes within a certain specified volume range (e.g.,about 1-5 nL), and the supplemental jetting may be performed by a secondejector configured to deposit viscous medium within another specifiedrange (e.g., about 5-15 nL) in order to deposit a total volume of about20 nL on a position on the surface of the workpiece where thesupplementary jetting of viscous medium may be performed simultaneouslyor on the fly, during the present printing process, or in an additional,supplementary printing process where the first ejector involved in a newjet printing job, for example, associated with a new separate board butperformed on the same working area of the jetting machine as the firstprinting process.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. An apparatus for at least one of depositing orjetting viscous medium on a surface of a workpiece, the apparatuscomprising: at least two depositing head assemblies, the at least twodepositing head assemblies including at least one jetting head assembly,or ejector, configured to perform jet printing of viscous medium,wherein the at least two depositing head assemblies are configured to bemutually different in shooting droplets with mutually different non-zeroshot sizes in a range of about 1-50 nL or within mutually different shotsize ranges of non-zero shot sizes in the range of about 1-50 nL, basedon the at least two depositing head assemblies causing respective nozzlespaces of the at least two depositing head assemblies to hold differentamounts of viscous medium prior to shooting droplets, the at least twodepositing head assemblies are further configured to move in threedimensional space and to at least one of concurrently or simultaneouslyjet or deposit the viscous medium on the workpiece, and at least onejetting head assembly of the at least two depositing head assemblies isconfigured to move while jetting the viscous medium on the workpiece. 2.The apparatus of claim 1, wherein the at least one jetting headassembly, or ejector, comprises: an impacting device configured torapidly build up a pressure impulse in a fluid chamber by rapid movementof the impacting device towards the fluid chamber, thereby forcingdroplets of the viscous medium through a nozzle of the at least onejetting head assembly, or ejector.
 3. The apparatus of claim 2, whereinthe impacting device includes a piezoelectric actuator.
 4. The apparatusof claim 1, wherein the at least two depositing head assemblies includeat least two jetting head assemblies; and the at least two jetting headassemblies are configured to jet droplets of viscous medium on theworkpiece, and move in three dimensions at least one of concurrently andsimultaneously.
 5. The apparatus of claim 1, further comprising: aplatform configured to hold the workpiece; a first beam arranged abovethe platform, a first depositing head assembly of the at least twodepositing head assemblies being movably fixed to the first beam; and asecond beam arranged above the platform and in parallel with the firstbeam, a second depositing head assembly of the at least two depositinghead assemblies being movably fixed to the second beam.
 6. The apparatusof claim 5, wherein the first depositing head assembly is configured tomove along the first beam in a first direction; and the seconddepositing head assembly is configured to move along the second beam inthe first direction.
 7. The apparatus of claim 6, wherein the first andsecond beams are configured to move in a second direction, which isperpendicular to the first direction.
 8. The apparatus of claim 7,wherein the first and second beams and the at least two depositing headassemblies are configured to move at least one of simultaneously andconcurrently.
 9. The apparatus of claim 8, wherein the first and seconddepositing head assemblies are configured to move in a third direction,which is perpendicular to the first and second directions.
 10. Theapparatus of claim 1, further comprising: a platform configured to holdthe workpiece; and a beam arranged above the platform, the at least twodepositing head assemblies being movably fixed to the beam.
 11. Theapparatus of claim 10, wherein the at least two depositing headassemblies are configured to move along the beam in a first direction.12. The apparatus of claim 10, wherein the beam is configured to move ina second direction.
 13. The apparatus of claim 10, wherein the beam andthe at least two depositing head assemblies are configured to move atleast one of simultaneously and concurrently.
 14. The apparatus of claim1, wherein a first depositing head assembly of the at least twodepositing head assemblies is configured to shoot droplets having avolume within a range of about 5-15 nL, and a second depositing headassembly of the at least two depositing head assemblies is configured toshoot droplets having a volume within a range of about 10-20 nL.
 15. Theapparatus of claim 1, wherein a first depositing head assembly of the atleast two depositing head assemblies is configured to shoot dropletshaving a volume within a range of about 1-5 nL, and a second depositinghead assembly of the at least two depositing head assemblies isconfigured to shoot droplets having a volume within a range of about10-20 nL.
 16. The apparatus of claim 1, wherein a first depositing headassembly of the at least two depositing head assemblies is configured toshoot droplets having a volume within a range of about 1-5 nL, and asecond depositing head assembly of the at least two depositing headassemblies is configured to shoot droplets having a volume within arange of about 5-15 nL.
 17. A method for at least one of depositing orjetting viscous medium on a workpiece, the method comprising: moving atleast two depositing head assemblies in three dimensional space; anddepositing the viscous medium on the workpiece by providing the at leasttwo depositing head assemblies to shoot droplets with at least one ofmutually different non-zero shot sizes in a range of about 1-50 nL orwithin mutually different shot size ranges of non-zero shot sizes in therange of about 1-50 nL, based on the at least two depositing headassemblies causing respective nozzle spaces of the at least twodepositing head assemblies to hold different amounts of viscous mediumprior to shooting droplets; wherein at least one of the at least twodepositing head assemblies is a jetting head assembly that moves whilejetting the viscous medium on the workpiece, and the at least twodepositing head assemblies move in three dimensional space by at leastone of concurrently and simultaneously jetting or depositing the viscousmedium on the workpiece.